Normal Oxygen Level (SpO₂) Calculator
Blood oxygen — SpO₂ — is the percentage of your red blood cells carrying oxygen. What counts as “normal” shifts a little with age, and drops predictably at altitude. Use the calculator to see a typical healthy range, then read the reference charts below.
Adult (18–64) · typical resting SpO₂
95–100%
At sea level, a healthy reading in this age group usually falls between 95% and 100%. Readings of 91–94% are borderline and worth watching; 90% or below is worth raising with a doctor, especially if it persists or comes with breathlessness.
Normal SpO₂ by age (sea level)
| Age group | Typical resting SpO₂ |
|---|---|
| Infant (under 1) | 95–100% |
| Child (1–12) | 97–100% |
| Teen (13–17) | 97–100% |
| Adult (18–64) | 95–100% |
| Older adult (65–79) | 94–99% |
| Elderly (80+) | 94–98% |
Expected SpO₂ by altitude
For a healthy person who has acclimatized. New arrivals typically read lower.
| Zone | Altitude | Expected SpO₂ |
|---|---|---|
| Sea level | 0 ft | ~98% |
| Low | 3,300 ft (1,000 m) | ~97% |
| Moderate | 6,600 ft (2,000 m) | ~94% |
| High | 8,200 ft (2,500 m) | ~93% |
| Very high | 11,500 ft (3,500 m) | ~88% |
| Extreme | 14,800 ft (4,500 m) | ~83% |
Frequently asked
What is a normal oxygen level by age?
For healthy people at sea level, a normal resting SpO₂ is 95–100% at essentially every age. Older and elderly adults sometimes sit slightly lower (around 94–98%) but 95% or above is still the general target. Readings of 91–94% are borderline, and 90% or below is worth discussing with a doctor.
What is a normal oxygen level at high altitude?
Oxygen in the air thins as you climb, so SpO₂ naturally drops with altitude. A healthy, acclimatized person might read around 94% at 6,600 ft, 90% at 9,800 ft and low-to-mid 80s above 14,000 ft. People who have just arrived often read lower until they adjust.
When is a blood oxygen reading too low?
As a general guide at normal altitude, below 90% is considered low and worth medical attention, and below 88% is often the threshold clinicians use for supplemental oxygen. Any reading paired with breathlessness, confusion or blue lips should be treated urgently. This calculator is informational and not a substitute for medical advice.
Keep reading
Want to watch SpO₂ continuously? A single reading is a snapshot. OxyRemote streams live SpO₂ and heart rate from a Bluetooth oximeter to your phone — and to family, anywhere — with an alert if it drops below a level you set. See how it works.
This calculator is for general information only and is not medical advice, diagnosis or a medical device. Normal ranges vary between individuals and health conditions. Always consult a qualified healthcare professional about your readings and never delay care based on this tool.